Spinal implants have been utilized for a number of years and typically comprise plates or rods affixed to the spine. For any number of reasons, a joint can deteriorate requiring an implant be inserted to various vertebrae.
A common practice has been to provide a pedicle screw in the individual vertebrae and attach a plate spanning the distance therebetween to stabilize the joint and maintain a set distance between the two vertebrae. The goal is to create/maintain normal anatomic relationship of two adjacent vertebrae of the spine. Often the plate is provided with at least one slot allowing for adjustment of the distance between the vertebrae before the implant is secured to the individual pedicle screws. The plate typically comprises a rigid material that will secure the vertebrae it is connected between. This configuration functions fairly well for securing one vertebrae to another.
However, a problem arises when multiple consecutive joints require stabilization. The problem arises due to the various anatomical differences that occur in the spine from patient to patient. For example, optimal pedicle screw spine fixation often requires that pedicle screws inserted into vertebrae are not oriented in a straight line. Therefore, connection of plates from one set of vertebrae to another requires that the plates be offset from one another, either medially or laterally, to maintain normal anatomic angular relationship of two adjacent vertebrae; or that the orientation of the pedicle screws in the vertebrae be adjusted.
The latter approach is disfavored as adjustment of vertebrae to line up the pedicle screws is highly undesirable and may not be possible, as is insertion of the pedicle screws in less optimal locations to achieve a relatively straight line.
Certain systems have been introduced to compensate for various anatomical differences with various levels of success. One such system includes an implantable device that is positioned between two vertebrae, such as for example, a wedge shaped device that is inserted in the location of where the spinal disc would normally reside. However, where removal of the disc is not required or advisable, this type of system is not usable.
In addition, minimal incision implantation is desired compared to open surgery. However, with the present systems, when multiple plates are used to span consecutive vertebrae, typically an incision is made to expose the entire area from vertebrae to vertebrae.